Question

我有一个嵌套的mysql查询，每6行给我一个表列（poutput_edat）的平均值

    set @rownum := 0;
    set @sum := 0;

    SELECT the_avg FROM (   
    select poutput_edat,   @rownum := (@rownum + 1) as rownum,    
    @sum := IF(@rownum mod 6 = 1,0 + poutput_edat,@sum + poutput_edat)
    as running_sum,   IF(@rownum mod 6 = 0,@sum / 6,NULL) as the_avg   
    from raw_edat /*WHERE date_edat = CURDATE()*/ ORDER BY invTime_edat desc)
    as average

我在使用php mysqli查询时遇到问题，它完全可以直接查询数据库。这是php mysql的限制吗？

麦

Answer 1

您可以尝试在单独的FROM子句中声明变量，例如：

SELECT the_avg FROM (   
    select poutput_edat,   @rownum := (@rownum + 1) as rownum,    
    @sum := IF(@rownum mod 6 = 1,0 + poutput_edat,@sum + poutput_edat)
    as running_sum,   IF(@rownum mod 6 = 0,@sum / 6,NULL) as the_avg   
    FROM raw_edat /*WHERE date_edat = CURDATE()*/, (SELECT @rownum := 0, @sum := 0) a 
    ORDER BY invTime_edat desc)
    as average

MySql嵌套选择，变量不适用于PHP

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